The extract of dendrobium Coelonin inhibits PIH induced by AFR CO2 fractional laser combined with UV-B.

Post-inflammatory hyperpigmentation (PIH) is a reaction process caused by an increase in melanin or abnormal melanin distribution due to inflammatory skin diseases, skin disease treatments, and external stimuli. Ultraviolet radiation can exacerbate PIH. It stimulates melanocytes, increases melanin production and deposition, and deepens the color and prolongs the duration of PIH. This study aims to investigate the inhibitory effects of Coelonin, an extract from Dendrobium officinale, on melanin production and its underlying mechanisms. Through molecular docking analysis, we found that Coelonin has significantly stronger binding capabilities to tyrosinase (TYR) and melanocortin 1 receptor (MC1R) than kojic acid, a well-known whitening agent. This stronger binding ability suggests that Coelonin may inhibit melanin production by regulating the activity of melanin metabolism-related proteins, thereby exerting its whitening effect. Compared with kojic acid, Coelonin demonstrates superior binding characteristics at the molecular level, providing stronger evidence for its potential as a whitening active ingredient. In cell experiments, Coelonin had no significant effect on the proliferation of B16-F10 melanoma cells within the concentration range of 20-40 µM, but it could significantly reduce the intracellular reactive oxygen species (ROS) levels and inhibit TYR activity and melanin production. Western blot results showed that Coelonin could downregulate the expression of TYR, MITF, TRP-1, and TRP-2 proteins. In in vivo experiments, a guinea pig model of PIH was established by Ablative Fractional Resurfacing CO₂ Laser (AFR CO2) combined with UV-B irradiation. It was found that Coelonin treatment could significantly improve skin pigmentation, reduce melanin granule deposition, and did not cause skin inflammation or hyperplasia and other side effects. This study indicates that Coelonin is an efficient and safe melanin synthesis inhibitor and has the potential to be developed as a plant-derived skin whitening agent.